The present invention pertains to an improved method for regenerating anion exchange resins loaded with organic compounds. More particularly, this method is useful to regenerate resins loaded with naphthenic acid and other organic acids.
Anion exchange resins are conventionally used to treat water. Organic substances present in the water accumulate on the ion exchange resin. These organic substances generally can include naphthenic acid, other organic acids, phenols, alcohols, pyridines, amines and organic sulfides. Over an extended period of operation, the ion exchange capacity of a resin declines significantly and some of the organic materials cannot be eluted by conventional methods.
Weak base ion exchange resins are conventionally used in the free base form of the amine to treat water. Caustic is commonly used to regenerate the resin by neutralization and displacement of organic compounds on the resin. However, it has been found that when an anion exchange resin has been loaded with naphthenic acid and like organic compounds, caustic treatment may restore significantly less than 90 percent of the original anion exchange capacity after repeated uses.
A variety of techniques have been proposed in the prior art for regeneration of ion exchange resins. Brine optionally with caustic has been used to regenerate ion exchange capacity. U.S. Pat. Nos. 3,536,637; 3,748,825 and 4,153,761 are illustrative of prior art techniques for removing organic compounds. U.S. Pat. No. 4,511,676 discloses that diethylene glycol compounds are particularly effective in restoring activity of ion exchange resins fouled with humic substances.
Anion exchange resins loaded with organic compounds in treating oil field waste waters are particularly difficult to regenerate. The relatively high concentrations of organic compounds encountered with oil field waters necessitates frequent regeneration of resins used in treating such waters. Moreover, the resistance of certain of these organic compounds to conventional methods of regenerating resins heretofore rendered the clean up of oil field waters with ion exchange resins impractical. A simple cost effective method for restoring the ion exchange capacity of resins adversely loaded with organic compounds is desired. Additionally, resins which efficiently remove organic compounds from waters produced in oil field operations and which can be regenerated readily are of practical and commercial interest.